1. Field of the Invention
This invention relates to devices for flushing indwelling vascular catheters, and more particularly to syringe tips that create vortex or helical flow of flushing media to dislodge accumulated debris from the tip of the indwelling catheter.
2. Background of the Invention
Vascular indwelling catheters or vascular access devices are used to inject medication, withdraw blood, or monitor functions within the blood vessel such as blood pressure and heart rate. The operation of catheters is often compromised or completely prevented by the occurrence of thrombus formation. Thrombosis is the development of a blood clot within a vessel and/or a catheter. Immediately after a catheter or other vascular access device is inserted into a blood vessel, a coagulation cascade begins. Platelets and white blood cells attach to the catheter surfaces. As the platelets begin to aggregate, fibrin strands form to cover the foreign object. The types of thrombotic occlusions that occur in indwelling catheters are intraluminal thrombus, mural thrombus, fibrin tail or flap, and fibrin sheath or sleeve.
Intraluminal thrombi develop when blood enters the lumen of the catheter. Mural thrombi develop when the tip of the catheter causes injury to the inner vascular wall. A mural thrombus is formed when the fibrin from the vessel wall injury attaches to the fibrin building on the catheter surface. The adherence of fibrin, blood cells, and platelets to the end or tip of a catheter is called a fibrin tail or flap. As the tail or flap attached to the catheter sticks out into the blood stream, more cells and other blood products become deposited onto the tail. A persistent withdrawal occlusion is caused by the fibrin flap acting as a one-way valve, allowing the catheter to flush easily, but not allowing blood to be aspirated. A fibrin sheath or sleeve is formed from adherence of fibrin to the external surfaces of the catheter. The sleeve may cover the terminal tip of the catheter, and extend up the entire length of the catheter, also causing persistent withdrawal occlusion.
The purpose of flushing is to clean the accumulated residue from the internal lumen of the catheter or from the catheter tip. The common practice is to create a turbulent flow during flushing to promote a xe2x80x9cscrubbingxe2x80x9d effect in the lumen and at the tip of the catheter. Turbulent flow is usually provided by pulsative flushing. This technique utilizes a xe2x80x9cstart-stopxe2x80x9d method that produces turbulence within the catheter lumen, reducing the potential for material to adhere to the catheter.
This xe2x80x9cstart-stopxe2x80x9d turbulent positive pressure flushing is difficult to perform effectively and must be performed in narrowly prescribed ways. Notwithstanding training and practice, the turbulence generated is random and dependent upon the internal diameter of the catheter and rate of the flow of the flushing media, in addition to other factors, such as the time interval between starting and stopping. Furthermore, because the turbulence by this method is generally not uniform across the internal diameter of the catheter, turbulent forces upon opposing internal walls of the catheter may be unequal, producing a whip-like effect or oscillations at the catheter tip. If the catheter tip moves with force, it can cause damage to the inner lining of the blood vessel wall leading to increased thrombus formation.
The present invention overcomes these problems of the relatively unpredictable results of start-stop flushing by providing a syringe tip that produces uniform predictable nonlaminar flow. This flow is in the form of a controlled uniform helical spiral or vortex flow, which effectively scrubs the debris from the lumens and tips of indwelling vascular catheters and related devices, avoiding the necessity of using the relatively crude and uncontrolled method of pulsatile flushing.
The present invention is a syringe tip that produces a nonlaminar helical or spiral flow of liquid as the liquid is injected through the tip with a syringe. When the syringe tip is inserted into the proximal end of a catheter, the spiral flow is transmitted along the length of the catheter whereby the spiral flow can scrub or dislodge blood deposits from the catheter lumen and catheter tip. The spiral or helical flow is produced by spiral elements on and/or in the inner wall or in the lumen of the syringe tip. The spiral flow created by the syringe tip makes the syringe tip useful for flushing vascular catheters without having to use the less reliable method of high pressure start-stop flushing.
An advantage of the present invention is that it provides a syringe tip that creates nonlaminar spiral flow of catheter flushing media.
Another advantage of the present invention is that it can be used to dislodge blood-derived deposits from the catheter lumen and/or catheter tip.
Another advantage of the present invention is that it produces effective flushing of vascular catheters without producing a random turbulent flow, thereby avoiding oscillations at the catheter tip which can damage the inner wall of a blood vessel.
Another advantage of the present invention is that the syringe tip can be permanently or removably attached to a syringe.
Another advantage of the present invention is that it requires no special training or practice for use in flushing vascular catheters.
Another advantage of the present invention is that it is simple and inexpensive to construct.
Another advantage of the present invention is it""s dual function: flushing vascular catheters and use in all other nonvascular syringe applications.